linux_dsm_epyc7002/include
David Rientjes ddbf369c0a mm, vmacache: hash addresses based on pmd
When perf profiling a wide variety of different workloads, it was found
that vmacache_find() had higher than expected cost: up to 0.08% of cpu
utilization in some cases.  This was found to rival other core VM
functions such as alloc_pages_vma() with thp enabled and default
mempolicy, and the conditionals in __get_vma_policy().

VMACACHE_HASH() determines which of the four per-task_struct slots a vma
is cached for a particular address.  This currently depends on the pfn,
so pfn 5212 occupies a different vmacache slot than its neighboring pfn
5213.

vmacache_find() iterates through all four of current's vmacache slots
when looking up an address.  Hashing based on pfn, an address has
~1/VMACACHE_SIZE chance of being cached in the first vmacache slot, or
about 25%, *if* the vma is cached.

This patch hashes an address by its pmd instead of pte to optimize for
workloads with good spatial locality.  This results in a higher
probability of vmas being cached in the first slot that is checked:
normally ~70% on the same workloads instead of 25%.

[rientjes@google.com: various updates]
  Link: http://lkml.kernel.org/r/alpine.DEB.2.21.1807231532290.109445@chino.kir.corp.google.com
Link: http://lkml.kernel.org/r/alpine.DEB.2.21.1807091749150.114630@chino.kir.corp.google.com
Signed-off-by: David Rientjes <rientjes@google.com>
Reviewed-by: Andrew Morton <akpm@linux-foundation.org>
Cc: Davidlohr Bueso <dave@stgolabs.net>
Cc: Alexey Dobriyan <adobriyan@gmail.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
2018-08-17 16:20:32 -07:00
..
acpi Merge branches 'acpi-x86', 'acpi-bus', 'acpi-ec' and 'acpi-apei' 2018-08-14 10:06:45 +02:00
asm-generic mm: provide a fallback for PAGE_KERNEL_EXEC for architectures 2018-08-17 16:20:29 -07:00
clocksource
crypto crypto: scatterwalk - remove scatterwalk_samebuf() 2018-08-03 18:06:04 +08:00
drm drm pull for 4.19-rc1 2018-08-15 17:39:07 -07:00
dt-bindings - xgene : potential null pointer fix 2018-08-16 10:16:08 -07:00
keys
kvm
linux mm, vmacache: hash addresses based on pmd 2018-08-17 16:20:32 -07:00
math-emu
media media: vsp1: Support Interlaced display pipelines 2018-08-03 16:02:27 -04:00
memory
misc
net Merge git://git.kernel.org/pub/scm/linux/kernel/git/davem/net-next 2018-08-15 15:04:25 -07:00
pcmcia
ras
rdma
scsi SCSI misc on 20180815 2018-08-15 22:06:26 -07:00
soc drivers: qcom: rpmh: add support for batch RPMH request 2018-07-21 13:33:36 -05:00
sound ASoC: Updates for v4.19 2018-08-13 12:12:31 +02:00
target scsi: target: add session removal function 2018-08-02 15:29:31 -04:00
trace Merge git://git.kernel.org/pub/scm/linux/kernel/git/davem/net-next 2018-08-15 15:04:25 -07:00
uapi pci-v4.19-changes 2018-08-16 09:21:54 -07:00
video drm: Add support for pps and compression mode command packet 2018-07-25 07:51:05 -04:00
xen xen/grant-table: Allow allocating buffers suitable for DMA 2018-07-26 23:05:14 -04:00